Systems designed to produce speed-responsive signals at predetermined rotational angles of a rotating machine have generally relied upon a sensor which initiates the process, by producing a signal referenced to a rotational angle of the machine. That signal has generally been produced in response to one or more indicia regularly angularly spaced on a rotating armature, the signal being produced when an indicia was close to the sensor. The indicia has typically taken the form of mechanical protrusions on a rotating wheel, a star wheel, or indentations in a rotating wheel, each indicia causing a corresponding signal used to produce a corresponding speed responsive signal. These indicia-forming projections are conventionally referred to as teeth, from their visual similarity to gear teeth.